Pumping system



y 1954 H. c. SWARTFIGUER PUMPING SYSTEM Filed April 8, 1952 Inventor":

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My 6 fm r c a t WWt A c ma e b P 6% Nb Patented July 13, 1954 PUMPING SYSTEM Herbert C. Swartfiguer, Niskayuna, N. Y., assignor to General Electric Company, a corporation of New York Application April 8, 1952, Serial No. 281,250

4 Claims.

This invention relates to a pumping apparatus and in particular to an improved pumping apparatus for a polymer such as polytetrafluoroethylene.

Wire used in the windings of transformers and other magnetic structures requires an insulation which will have desirable electrical properties and a minimum wall thickness to reduce bulk. One of the more modern insulation materials for such wire, hereinafter called magnet wire, is a polytetrafluoroethylene coating in the nature of a paint or varnish. This. material, in one form is sold under the trade name of Teflon by the E. I. du Pont de Nemours Company.

It is not intended that this invention should be limited simply to an apparatus for pumping polytetrafluoroethylene or any other particular polymer because the apparatus will work equally well with many polymers and coagulative dispersions. For the sake of ease of description, however, the apparatus Will be described in conjunction with a polymer.

Polymers for use as magnet wire insulation are received as water dispersions which cannot be pumped by ordinary means. That is, if the water dispersion is run through a gear pump it tends to coagulate; it will foam and. coagulate if agitated violently as would be the situation if it were handled by a centrifugal pump. So, too, the action or a ball valve or any similar squeezing of the material between two solid materials tends to coagulate it.

Accordingly, it is an object of this invention to provide an improved pumping system for polymers and other coagulative dispersions.

It is a further object of this invention to pro vide an improved inexpensive pumping system whereby polymers and other similar materials may be pumped without coagulation or foaming.

It is a further object of this invention to provide an improver pumping system for cyclically supplying polymers or other similar material to .a wire coating apparatus.

flow path in combination with suitable valves and a cyclically applied air pressure supply for the intermittent circulation of a polymer type material to a wire coating mechanism.

In one method of applying a polymer to a wire, the wire I is passed through a bath or applicator 2 containing a water dispersion of the polymer. The wire picks up a thin film which is then baked in ovens (not shown) to form a flexible enameled coating. Obviously, the wire can be passed through the bath as many times as necessary to pick up the desired thickness of the polymer.

The problem encountered in this application is to maintain the polymer in a constant state of change to prevent the water dispersion from settling out; that is, the polymer-water dispersion must be circulated through the applicator for the dispersion to retain its desired flexible insulating properties.

It has been pointed out that a polymer suspension cannot be pumped by ordinary mechanical devices, otherwise it will either coagulate or foam. My improved pumping system which prevents coagulation and foaming comprises in addition to applicator 2, a storage tank 3, an anti-flow-back device 4, a return tank 5, a solenoid operated valve 6 for supplying air to the storage tank 3 and a timer 1 for controlling the flow of air through the solenoid valve 5.

Storage tank 3 can be of any suitable size and material providing the material is compatible with the polymer. Glass is one example of such a material, and in the illustrated embodiment a glass jar 3a is fitted with a tight cover 3 punctured to receive tubes 9, it and i l and then sealed to" prevent leakage. Tube 8 interconnects storage tank 3 with anti-iiowbaek device t. The latter comprises a storage jar i2, similar to storage tank 3, having a cover 53 apertured and sealed as is cover 8 to receive tubes 9 and i4. Tube M interconnects anti-floW-back device t with the applicator 2, which in turn is interconnected by means of tube It to return tank 5. Return tank 5, which may be physically similar to tanks 3a and I2 is then interconnected by return line or tube It to the storage tank a.

' The interconnected system described and illustrated in the drawing is so constructed that when air is forced through tube ll, which connects the storage tank 3 with an external air supply, the air tends to displace the polymer from tank 3 into tubes 9 and it and thereby force the liquid material into both the anti-flow-bmk device 4 and return tank 5. To prevent the polymer from flowing up into tube it, a quantity of mercury IE3 is placed in the bottom of storage tank 3 to a depth that just covers the end of tube lil. Under these circumstances when air is forced into tube H, th pressure will act on the polymer and force it up into tube 9 which does not extend as far into the tank 3 as does tube [3. The air pressure in tank 3, simultaneously will force mercury is into tube is to act as a valve thereby preventing the polymer from flowing up into the return tank a Obviously, the mercury will rise only a few inches in the tube Iii when a pressure, in the order of say thirty inches of water is used to force the polymer from storage tank 3 to anti-fiow-back device 4.

To prevent liquid now from anti-fiow-back device a to tank 3, a second valve is provided by a quantity of mercury ll positioned to cover the end of tube 9 within jar :2. The function of the mercury l? is similar to the mercury [6; that is, under pressure conditions wherein there is a greater pressure in tube It than in tube 9 the mercury will flow into the end or" tube 8 and act as a valve. The mercury pool ll will also prevent siphoning of the polymer into the storage tank 3 when pressure is taken off tube 5 l.

This structure provides a basic flow path. for the polymer wherein, under suitable pressure conditions, the polymer flows through tube 9 from tank to anti-fiow-back device i, through the mercury El and through tube i l to the applicator 2. The polymer is then free to flow by gravity from the applicator through tube 15 to return tank 5.

It has already been stated that when the air pressure is raised in tube ii, the mercury pool is is forced up into tube ill to act as a valve thereby preventing the flow of the polymer from storage tank 3 to the return tank 5. This same mercury pool serves a dual function in that it prevents the siphoning or gravity flow of the polymer from return tank 5 to the storage tank 3 when the pressure is raised in tube H. When air pressure is released from the tube ii, how ever, the mercury pool it will settle to its normal level and the polymer will flow from return tank 5 through tube it into storage tank 3. The polymer will bubble through the mercury pool 5 to refill the storage tank 15 and tube ll up to the level of the return tank 5.

Since the polymer in the storage tank 3 must be replenished periodically from the return tank 5, it is advantageous to provide a mechanical means for supplying an intermittent flow of air through tube ll into storag tank Such a mechanical means is accomplished in the illustrated embodiment by a solenoid valve 6 which is positioned to interconnect tube H with an air supply line l8. When solenoid valve 6 is open, the outlet valve 59 is closed to the atmosphere and the air from supply line it; passes through the valve into tube ii, and thence into storage tank 3. When valve 5 is closed, the outlet tube 59 is opened to the atmosphere whereby the air contained in storage tank 3 can flow through tube 2 l and to the atmosphere.

While a solenoid valve has been illustrated, and while its operation will hereinafter be described, it is to be understood that other pumping devices, for example, a diaphragm pump of the automobile fuel pump variety will also function satisfactorily to furnish an intermittent supply of air to storage tank 3.

For the cyclic opening of solenoid valve 6, which has an operating coil 28, a switch 2| is positioned in one of the conductors connecting coil 20 to a power line 22. The closing of switch 2|, in turn, is controlled by a timer 7 driven from the power line 22. The timer has a cam 23 positioned to act on a cam follower 24 to close the contacts of switch 2| at every revolution of the cam 23. Obviously, the time of closing of th contacts 2! and the rate of rotation of the cam 23 can be controlled by simple mechanical arrangements.

With the position of the elements of this apparatus as shown in the drawing, the contacts of switch 23 are open, coil 2b is (lo-energized, solenoid valve 6 is closed and tube is interconnectstube H with the atmosphere. Accordingly, since there is atmospheric pressure within the storage tank 3, the mercury pool It has fallen to its normal level and the polymer flows by gravity from return tank 5, through tube It, bubbles through the mercury l3 and up into tube 1 I until it reaches a level as determined by liquid level in return tank 5.

When timer 7 drives cam 23 to position where it acts on cam follower 2A to close the contacts of switch 2!, coil 29 is energea, solenoid valve 6 is opened and air flows from air supply line lS, through valve E5, tube it into storage tank 3. The air then acts upon the polymer within storage tank 3, forces the mercury it up into tube i!) and pushes the polymer through tube into anti-flowback device 41, through the mercury pool i"! intotube i l and then into the applicator 2. The polymer will flow from storage tank 3 so long as air pressure is applied or until its level recedes below the end of tube 9. Accordingly, the air pressure, controlled by cam 23, is timed for a flow of a pre determine-d quantity of the polymer from storage tank tto the applicator 2. At the elapse of this predetermined period, the cam 23 releases follower 2 to open the contacts of switch 2 l; solenoid valve 23 is then closed and tube H is again interconnectedwith the atmospherethrough tube 19. Under these conditions, the mercury pool l6 recedes to its normal level the polymer, which has moved by gravity from the applicator 2 into return tank 5, returns to storage tank 3 and. rises in tube l to a level which is determined by the head of the polymer in the return tank 5.

It has been found that this embodiment of the pumping system has worked very well in supplying a water dispersed polymer to an applicator, but it is obvious that other modifications of this apparatus will occur to those skilled in the art and, it is desired to be understood, therefore, that thisinvention is not to to the particular embodiment disclosed but rather it is intended to cover all modifications which are within the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An improved polymer pumping apparatus comprising a storage tank having an inlet tube, an outlet tube and a return tube therein, the end of said return tube being positioned nearer the bottom of said tank than the end of said outlet tube, a pressure tight cover for said tank apertured and sealed to receive said tubes, a quantity of mercury in the bottom of said storage tank to cover the end of said return tube, an applicator tank, tube means connecting said applicator tank to-said outlet tube and means for cyclically supplying air pressure to said storage tank through said inlet tube to-force said mercury into said return tube and. close the return tube from flow of said polymer therethrough and to force said polymer through said outlet tube to said applicator tank.

2. An improved polymer pumping apparatus comprising a storage tank having an inlet tube, an outlet tube and a return tube therein, a pressure tight cover for said tank apertured and sealed to receive said tubes, a quantity of mercury in the bottom of said storage tank to cover the end of said return tube, an anti-flow-back tank, first tube means interconnecting said anti-flowback tank with said "outlet tube of said storage tank, a quantity of mercury covering the end of ,said tube means in said anti-flow-back tank, an

applicator tank, second tube means interconnecting said anti-flow-back tank with said applicator tank and means for supplying air pressure to said storage tank through said inlet tube to force said mercury into said return tube and said polymer through said outlet tube to said applicator tank through said anti-flow-back tank.

3. An improved polymer pumping apparatus comprising a storage tank having an inlet tube, an outlet tube and a return tube therein, a pressure tight cover for said tank apertured and sealed to receive said tubes, a quantity of mercury in the bottom of said storage tank to cover the end of said return tube, an anti-flow-back tank, first tube means interconnecting said anti-flowback tank with said outlet tube of said storage tank, a quantity of mercury covering the end of said first tube means in said anti-flow-back tank, an applicator tank, second tube means interconnecting said anti-fi'ow-loack tank with said applicator tank and means for cyclically supplying air pressure to said storage tank through said inlet tube to force said mercury into said return tube and said polymer through said outlet tube to said applicator tank, said pressure means comprising a solenoid operated air valve having an 4. An improved apparatus for pumping a liqbeing positioned nearer the bottom of said tank than the end of said outlet tube, a pressure tight cover .for said tank apertured and sealed to re-' ceive said tubes, a quantity of mercury in the bottom of said storage tank to cover the end of said return tube, an applicator tank, tube means connecting said applicator tank to said outlet tube, and means for supplying air pressure to said storage tank through said inlet tube to force said mercury into said return tube and close the return tube from flow of said liquid dispersion therethrough and to force said liquid dispersion through said outlet tube to said applicator tank.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 49,063 Atwater Aug. 1, 1865 127,592 Gates June 4, 1872 631,732 Wristen Aug. 22, 1899 968,664 Humphrey Aug. 30, 1910 2,127,413 Leguillon Aug. 16, 1938 2,545,445 Chatterton Mar. 20, 1951 

